Microgel Insulin Delivery System Mimics Beta-Cell Action

Diabetes researchers have developed a nanotech technique to transport insulin in the bloodstream and release or sequester the hormone in response to changes in blood sugar levels.

Investigators at the University of North Carolina (Chapel Hill, USA) and their colleagues at the Massachusetts Institute of Technology (Cambridge, USA) used a one-step electrospray procedure to fabricate monodisperse microgels consisting of a pH-responsive chitosan matrix, enzyme nanocapsules, and recombinant human insulin. Glucose-specific enzymes were covalently encapsulated into the nanocapsules to improve enzymatic stability by protecting from denaturation and immunogenicity as well as to minimize loss due to diffusion from the matrix.

The microgel system swelled and released insulin when subjected to hyperglycemic conditions, as a result of the enzymatic conversion of glucose into gluconic acid and protonation of the chitosan network. The microgels acted as a self-regulating valve system by secreting insulin at basal release rates under normoglycemic conditions and at higher rates under hyperglycemic conditions.

Results published in the July 8, 2013, online edition of the journal ACS Nano revealed that in a mouse model of type I diabetes microgel-facilitated insulin release caused a reduction of blood glucose levels that lasted for more than 48 hours.

“The chitosan itself can be absorbed by the body, so there are no long term health effects,” said first author Dr. Zhen Gu, assistant professor of biomedical engineering the University of North Carolina. “We wanted to mimic the function of healthy beta-cells, which produce insulin and control its release in a healthy body, but what we have found also holds promise for smart drug delivery targeting cancer or other diseases.”